Dietary fatty acids and the aging brain

Brain Healthcare Quotient as a Tool for Standardized Approach in Brain Healthcare Interventions

In addressing the challenge of assessing healthy brain aging across diverse interventions, this study introduces the use of MRI-derived Brain Healthcare Quotients (BHQ) for comprehensive evaluation. We analyzed BHQ changes in 319 participants aged 24-69, who were allocated into dietary (collagen peptide, euglena, matcha, isohumulone, xanthophyll) and physical activity (hand massage with lavender oil, handwriting, office stretching, pink lens, clinical art) groups, alongside a control group, over a month. These interventions were specifically chosen to test the efficacy of varying health strategies on brain health, measured through BHQ indices: GM-BHQ for gray matter volume, and FA-BHQ for white matter integrity. Notably, significant improvements in FA-BHQ were observed in the collagen peptide group, with marginal increases in the hand massage and office stretching groups. These findings highlight BHQ's potential as a sensitive tool for detecting brain health changes, offering evidence that low-intensity, easily implemented interventions can have beneficial effects on brain health. Moreover, BHQ allows for the systematic evaluation of such interventions using standard statistical approaches, suggesting its value in future brain healthcare research.

Relationship between fatty acid intake and aging: a Mendelian randomization study

BACKGROUND

Observational studies have previously shown a possible link between fatty acids and aging-related diseases, raising questions about its health implications. However, the causal relationship between the two remains uncertain.

METHODS

Univariable and multivariable Mendelian randomization (MR) was used to analyze the relationship between five types of fatty acids-polyunsaturated fatty acid (PUFA), monounsaturated fatty acid (MUFA), saturated fatty acid (SFA), Omega-6 fatty acid (Omega-6 FA), and Omega-3 fatty acid (Omega-3 FA) and three markers of aging: telomere length (TL), frailty index (FI), and facial aging (FclAg). The primary approach for Mendelian randomization (MR) analysis involved utilizing the inverse variance weighted (IVW) method, with additional supplementary methods employed.

RESULTS

Univariate MR analysis revealed that MUFA, PUFA, SFA, and Omega-6 fatty acids were positively associated with TL (MUFA OR: 1.019, 95% CI: 1.006-1.033; PUFA OR: 1.014, 95% CI: 1.002-1.026; SFA OR: 1.016, 95% CI: 1.002-1.031; Omega-6 FAs OR=1.031, 95% CI: 1.006-1.058). PUFA was also associated with a higher FI (OR: 1.033, 95% CI: 1.009-1.057). In multivariate MR analysis, after adjusting for mutual influences among the five fatty acids, MUFA and PUFA were positively independently associated with TL (MUFA OR: 1.1508, 95% CI = 1.0724-1.2350; PUFA OR: 1.1670, 95% CI = 1.0497-1.2973, while SFA was negatively correlated (OR: 0.8005, 95% CI: 0.7045-0.9096).

CONCLUSIONS

Our research presents compelling evidence of a causal association between certain fatty acids and indicators of the aging process. In particular, MUFA and PUFA may play a role in slowing down the aging process, while SFAs may contribute to accelerated aging. These findings could have significant implications for dietary recommendations aimed at promoting healthy aging.

Concurrent training associated with moderate walnut consumption improved isokinetic strength, subjective sleep quality, cognitive performance and postural balance in elderly active men: a randomized controlled trial

AIMS

To investigate the effects of concurrent training (resistance and endurance) associated with moderate walnut consumption on isokinetic strength, subjective sleep quality, cognitive performance and postural balance in physically active elderly men.

METHODS

Twenty healthy elderly men were divided into two matched groups, in a randomized controlled experiment. They have participated in three training sessions per week: concurrent (strength and endurance) training + ad libitum diet with walnuts (15 g/day for 6 weeks, CTW: n = 10) and concurrent training + ad libitum diet (CT: n = 10). Isokinetic strength, Spiegel questionnaire, Montreal cognitive assessment and postural balance parameters were assessed 48 h pre- and post-intervention.

RESULTS

Absolute peak torque of knee extensors and knee flexors significantly increased compared to pre-training in CTW (15.2% ± 6.7; 13.2% ± 2.3, p < 0.05, respectively) and CT (10.6% ± 6.8; 7.4% ± 2.9, p < 0.05, respectively). Subjective sleep quality increased compared to pre-training for CTW and CT (24% ± 14.4; 10.5% ± 9.4, p < 0.05, respectively) with a significantly greater increase in CTW (p < 0.05). Cognitive performance measured by Montreal cognitive assessment (MoCA) increased only in CTW compared to baseline (7.7% ± 2.5, p < 0.05). Postural balance parameters with dual task decreased only in CTW compared to baseline.

CONCLUSIONS

The present study clearly revealed that concurrent training alone or associated with daily walnut (15 g) consumption for 6 weeks significantly increased knee isokinetic strength, support leg standing parameters and sleep quality. Meanwhile, cognitive performance evaluated by MoCA test and postural balance with dual task were improved for CTW group only.

Metabolic Syndrome as a Risk Factor for Alzheimer's Disease: A Focus on Insulin Resistance

Alzheimer's disease (AD) is the main type of dementia and is a disease with a profound socioeconomic burden due to the lack of effective treatment. In addition to genetics and environmental factors, AD is highly associated with metabolic syndrome, defined as the combination of hypertension, hyperlipidemia, obesity and type 2 diabetes mellitus (T2DM). Among these risk factors, the connection between AD and T2DM has been deeply studied. It has been suggested that the mechanism linking both conditions is insulin resistance. Insulin is an important hormone that regulates not only peripheral energy homeostasis but also brain functions, such as cognition. Insulin desensitization, therefore, could impact normal brain function increasing the risk of developing neurodegenerative disorders in later life. Paradoxically, it has been demonstrated that decreased neuronal insulin signalling can also have a protective role in aging and protein-aggregation-associated diseases, as is the case in AD. This controversy is fed by studies focused on neuronal insulin signalling. However, the role of insulin action on other brain cell types, such as astrocytes, is still unexplored. Therefore, it is worthwhile exploring the involvement of the astrocytic insulin receptor in cognition, as well as in the onset and/or development of AD.

Type 2 Diabetes and Alzheimer's Disease: The Emerging Role of Cellular Lipotoxicity

Type 2 diabetes (T2D) and Alzheimer's diseases (AD) represent major health issues that have reached alarming levels in the last decades. Although growing evidence demonstrates that AD is a significant comorbidity of T2D, and there is a ~1.4-2-fold increase in the risk of developing AD among T2D patients, the involvement of possible common triggers in the pathogenesis of these two diseases remains largely unknown. Of note, recent mechanistic insights suggest that lipotoxicity could represent the missing ring in the pathogenetic mechanisms linking T2D to AD. Indeed, obesity, which represents the main cause of lipotoxicity, has been recognized as a major risk factor for both pathological conditions. Lipotoxicity can lead to inflammation, insulin resistance, oxidative stress, ceramide and amyloid accumulation, endoplasmic reticulum stress, ferroptosis, and autophagy, which are shared biological events in the pathogenesis of T2D and AD. In the current review, we try to provide a critical and comprehensive view of the common molecular pathways activated by lipotoxicity in T2D and AD, attempting to summarize how these mechanisms can drive future research and open the way to new therapeutic perspectives.

Age-associated changes in circulatory fatty acids: new insights on adults and long-lived individuals

Long-lived individuals (LLIs) are considered an ideal model to study healthy human aging. Blood fatty acid (FA) profile of a cohort of LLIs (90-111 years old, n = 49) from Sicily was compared to adults (18-64 years old, n = 69) and older adults (65-89 years old, n = 54) from the same area. Genetic variants in key enzymes related to FA biosynthesis and metabolism were also genotyped to investigate a potential genetic predisposition in determining the FA profile. Gas chromatography was employed to determine the FA profile, and genotyping was performed using high-resolution melt (HRM) analysis. Blood levels of total polyunsaturated FA (PUFA) and total trans-FA decreased with age, while the levels of saturated FA (SFA) remained unchanged. Interestingly, distinctively higher circulatory levels of monounsaturated FA (MUFA) in LLIs compared to adults and older adults were observed. In addition, among LLIs, rs174537 in the FA desaturase 1/2 (FADS1/2) gene was associated with linoleic acid (LA, 18:2n-6) and docosatetraenoic acid (DTA, 22:4n-6) levels, and the rs953413 in the elongase of very long FA 2 (ELOVL2) was associated with DTA levels. We further observed that rs174579 and rs174626 genotypes in FADS1/2 significantly affect delta-6 desaturase (D6D) activity. In conclusion, our results suggest that the LLIs have a different FA profile characterized by high MUFA content, which indicates reduced peroxidation while maintaining membrane fluidity.

Ecological lipidology

Dietary lipids (DLs), particularly sterols and fatty acids, are precursors for endogenous lipids that, unusually for macronutrients, shape cellular and organismal function long after ingestion. These functions – cell membrane structure, intracellular signalling, and hormonal activity – vary with the identity of DLs, and scale up to influence health, survival, and reproductive fitness, thereby affecting evolutionary change. Our Ecological Lipidology approach integrates biochemical mechanisms and molecular cell biology into evolution and nutritional ecology. It exposes our need to understand environmental impacts on lipidomes, the lipid specificity of cell functions, and predicts the evolution of lipid-based diet choices. Broad interdisciplinary implications of Ecological Lipidology include food web alterations, species responses to environmental change, as well as sex differences and lifestyle impacts on human nutrition, and opportunities for DL-based therapies.

Dietary Alterations in Impaired Mitochondrial Dynamics Due to Neurodegeneration

Alzheimer's disease is still an incurable disease with significant social and economic impact globally. Nevertheless, newly FDA-approved drugs and non-pharmacological techniques may offer efficient disease treatments. Furthermore, it is widely accepted that early diagnosis or even prognosis of Alzheimer's disease using advanced computational tools could offer a compelling alternative way of management. In addition, several studies have presented an insight into the role of mitochondrial dynamics in Alzheimer's development. In combination with diverse dietary and obesity-related diseases, mitochondrial bioenergetics may be linked to neurodegeneration. Considering the probabilistic expectations of Alzheimer's disease development or progression due to specific risk factors or biomarkers, we designed a Bayesian model to formulate the impact of diet-induced obesity with an impaired mitochondrial function and altered behavior. The applied probabilities are based on clinical trials globally and are continuously subject to updating and redefinition. The proposed multiparametric model combines various data types based on uniform probabilities. The program simulates all the variables with a uniform distribution in a sample of 1000 patients. First, the program initializes the variable age (30-95) and the four different diet types ("HFO_diet," "Starvation," "HL_diet," "CR") along with the factors that are related to prodromal or mixed AD (ATP, MFN1, MFN2, DRP1, FIS1, Diabetes, Oxidative_Stress, Hypertension, Obesity, Depression, and Physical_activity). Besides the known proteins related to mitochondrial dynamics, our model includes risk factors like Age, Hypertension, Oxidative Stress, Obesity, Depression, and Physical Activity, which are associated with Prodromal Alzheimer's. The outcome is the disease progression probability corresponding to a random individual ID related to diet choices and mitochondrial dynamics parameters. The proposed model and the programming code are adjustable to different parameters and values. The program is coded and executed in Python and is fully and freely available for research purposes and testing the correlation between diet type and Alzheimer's disease progression regarding various risk factors and biomarkers.

Altered Metabolism in Alzheimer Disease Brain: Role of Oxidative Stress

Significance: Alzheimer disease (AD) is an all-too-common condition in the aging population. However, aging does not automatically equal neurodegeneration and memory decline. Recent Advances: This review article involves metabolic changes in the AD brain that are related to oxidative stress. Selected pathways are identified as potential targets for intervention in AD. Critical Issues: One of the main factors of AD is the oxidative imbalance within the central nervous system, causing a disruption in metabolic processes. Reactive oxygen species (ROS) are a natural consequence of many cellular processes, especially those associated with mitochondria, such as the electron transport chain. Some ROS, when kept under control and maintained at reasonable levels, often play roles in cell signaling. The cellular damage of ROS arises when oxidative imbalance occurs, in which case ROS are not controlled, leading to a myriad of alterations in cellular metabolic processes. These altered pathways include, among others, dysfunctional glycolysis, calcium regulation, lipid metabolism, mitochondrial processes, and mammalian target of rapamycin pathway dysregulation. Future Directions: Understanding how ROS can lead to these alterations can, ideally, elucidate therapeutic options for retarding AD progression in the aging population. Antioxid. Redox Signal. 36, 1289-1305.

Exogenous lipase administration alters gut microbiota composition and ameliorates Alzheimer's disease-like pathology in APP/PS1 mice

Alzheimer's disease (AD) represents the most common form of dementia in the elderly with no available disease modifying treatments. Altered gut microbial composition has been widely acknowledged as a common feature of AD, which potentially contributes to progression or onset of AD. To assess the hypothesis that Candida rugosa lipase (CRL), which has been shown to enhance gut microbiome and metabolite composition, can rebalance the gut microbiome composition and reduce AD pathology, the treatment effects in APPswe/PS1de9 (APP/PS1) mice were investigated. The analysis revealed an increased abundance of Acetatifactor and Clostridiales vadin BB60 genera in the gut; increased lipid hydrolysis in the gut lumen, normalization of peripheral unsaturated fatty acids, and reduction of neuroinflammation and memory deficits post treatment. Finally, we demonstrated that the evoked benefits on memory could be transferred via fecal matter transplant (FMT) into antibiotic-induced microbiome-depleted (AIMD) wildtype mice, ameliorating their memory deficits. The findings herein contributed to improve our understanding of the role of the gut microbiome in AD's complex networks and suggested that targeted modification of the gut could contribute to amelioration of AD neuropathology.

It Is Time for an Oil Change: Polyunsaturated Fatty Acids and Human Health

Polyunsaturated fatty acids (PUFAs) such as docosahexaneoic acid (DHA) and eicosapentaneoic acid (EPA), play a critical role in a variety of neuronal functions, including facilitating neuronal growth and differentiation, increasing the density of the neuritic network, modulating cell membrane fluidity, regulating intracellular signaling and gene expression, and exhibiting antioxidant characteristics. Dietary DHA is selectively enriched and actively retained in the central nervous system, mainly in synaptic membranes, dendrites, and photoreceptors. In this review, we highlight the myriad roles of PUFAs in brain function and human health. Diets rich in DHA are inversely proportional to cognitive decline and incidence of neurodegenerative disorders. Conversely, diets deficient in DHA impair the proper development of brain and the visual system in children and increase risk of brain disorders in the elderly. Finally, DHA and EPA have been shown to reduce inflammation and may prove to be beneficial in reducing the severity of the SARS-COVID infection.

LPC-DHA/EPA-Enriched Diets Increase Brain DHA and Modulate Behavior in Mice That Express Human APOE4

Compared with APOE3, APOE4 is associated with greater age-related cognitive decline and higher risk of neurodegenerative disorders. Therefore, development of supplements that target APOE genotype-modulated processes could provide a great benefit for the aging population. Evidence suggests a link between APOE genotype and docosahexaenoic acid (DHA); however, clinical studies with current DHA supplements have produced negative results in dementia. The lack of beneficial effects with current DHA supplements may be related to limited bioavailability, as the optimal form of DHA for brain uptake is lysophosphatidylcholine (LPC)-DHA. We previously developed a method to enrich the LPC-DHA content of krill oil through lipase treatment (LT-krill oil), which resulted in fivefold higher enrichment in brain DHA levels in wild-type mice compared with untreated krill oil. Here, we evaluated the effect of a control diet, diet containing krill oil, or a diet containing LT-krill oil in APOE3- and APOE4-targeted replacement mice (APOE-TR mice; treated from 4 to 12 months of age). We found that DHA levels in the plasma and hippocampus are lower in APOE4-TR mice and that LT-krill oil increased DHA levels in the plasma and hippocampus of both APOE3- and APOE4-TR mice. In APOE4-TR mice, LT-krill oil treatment resulted in higher levels of the synaptic vesicle protein SV2A and improved performance on the novel object recognition test. In conclusion, our data demonstrate that LPC-DHA/EPA-enriched krill oil can increase brain DHA and improve memory-relevant behavior in mice that express APOE4. Therefore, long-term use of LT-krill oil supplements may on some level protect against age-related neurodegeneration.

Omega-3 Long-Chain Polyunsaturated Fatty Acids: Are They Beneficial for Physical and Cognitive Functioning in Older Adults?

BACKGROUND

There is equivocal evidence about beneficial properties of omega-3 long-chain polyunsaturated fatty acids (ω-3 LCPUFA) for older adults.

OBJECTIVE

This study investigated the relationship between circulating ω-3 LCPUFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels and their corresponding dietary intakes with cognition and physical function in a cohort of community-dwelling older adults at risk of dementia.

METHODS

A cross-sectional analysis was conducted among 142 community-dwelling older adults (60-85 years) with subjective memory complaints. Erythrocyte fatty acids (ω-3 LCPUFA) and the omega-3 index were measured; dietary DHA and EPA were assessed with a LCPUFA specific questionnaire. Cognition was measured using the Cogstate computerised battery and Trail-making tests. Muscle strength was assessed by grip strength and physical function via the four-square step test, 30-second sit-to-stand, timed up-and-go test, and 4-m walk test. Multiple regression analysis was used to assess the relationship between erythrocyte ω-3 LCPUFA, dietary intake, cognitive and physical function.

RESULTS

Higher dietary DHA and EPA were associated with better global cognitive function (DHA: β=0.164, p=0.042; EPA: β=0.188, p=0.020). Higher dietary EPA was associated with better attention/psychomotor composite scores (β=0.196, p=0.024), mobility (four-square step test: β=-0.202, p=0.015) and gait speed (4m walk test: β=-0.200, p=0.017). No associations were found between erythrocyte ω-3 LCPUFA and cognitive or functional performance measures.

CONCLUSIONS

In community-dwelling older adults with subjective memory complaints, higher dietary ω-3 LCPUFA intake was associated with better cognitive and physical function, supporting the evidence that ω-3 fatty acids play a role in optimising physical and cognitive health during ageing.

The Impact of Gut Microbiota Disorders on the Blood-Brain Barrier

The gut microbiota is symbiotic with the human host and has been extensively studied in recent years resulting in increasing awareness of the effects of the gut microbiota on human health. In this review, we summarize the current evidence for the effects of gut microbes on the integrity of the cerebral blood-brain barrier (BBB), focusing on the pathogenic impact of gut microbiota disorders. Based on our description and summarization of the effects of the gut microbiota and its metabolites on the nervous, endocrine, and immune systems and related signaling pathways and the resulting destruction of the BBB, we suggest that regulating and supplementing the intestinal microbiota as well as targeting immune cells and inflammatory mediators are required to protect the BBB.

In silico and in vitro evaluation of brain penetration properties of selected nootropic agents

Aim: Predictive ( in silico) data suggested that nootropic supplements may penetrate the blood–brain barrier (BBB). We evaluated, in vitro, the ability of nootropics to enter the brain based on the high throughput screening (HTS) measurement of interactions with the P-gp efflux transporter and physicochemical properties and correlated these data with the in silico predictions. Methods & results: The software predicted that piracetam, docosahexaenoic acid (DHA), amantadine and thioflavin-T can best penetrate the BBB. The lipophilicity of these compounds may be predicted by measuring the critical micelle concentration (CMC). DHA and verapamil demonstrated high lipophilicity. DHA, verapamil and phosphatidylserine (PS) may be good substrates of the P-gp transporter. Conclusion: Permeability of nootropics may be successfully predicted by high throughput screening-lead optimization assay technologies.

Docosahexaenoic acid (22:6n-3) Ameliorated the Onset and Severity of Experimental Autoimmune Encephalomyelitis in Mice

Multiple sclerosis (MS) is a neurologic autoimmune disease, which is the leading cause of nontraumatic neurologic disability in young adults in United States and Europe. n-3 polyunsaturated fatty acids (PUFA) are reported to mitigate severity of this disease. Recent studies suggest that phospholipid (PL) form of dietary n-3 PUFA may lead to their higher tissue accretion than triacylglycerol (TAG) form. We compared efficacy of PL-docosahexaenoic acid (22:6n-3) (DHA) and TAG-DHA on onset and severity of experimental autoimmune encephalomyelitis (EAE) in a mouse model of MS. Female mice were fed low alpha-linolenic acid (18:3n-3) (ALA) diet (control) for 2 weeks and then fed either control, 0.3%, or 1.0% DHA (PL or TAG) for 4 weeks pre-EAE induction and 4 weeks post-EAE induction. The brain and spinal cord n-6:n-3 ratio was significantly lower in all mice fed DHA compared to control. EAE onset was delayed in mice fed both DHA forms and concentrations, except for 1% TAG-DHA. The inverse association between the EAE score and the brain DHA concentration was nonsignificant at the end of the study (p = 0.08). Daily EAE scores of mice fed different DHA diets did not differ from control, however, the score of all DHA groups combined during days 9-16 was lower (p = 0.028) compared to the control. During days 17-22, the EAE score trended lower in 0.3% TAG-DHA and during days 23-28, the EAE score trended lower in both PL-DHA groups than those in all other groups. These findings suggest that TAG-DHA may be more effective than PL-DHA in the early phases of EAE, and in the final outcome, PL-DHA may be more effective than TAG-DHA.

Japanese, Mediterranean and Argentinean diets and their potential roles in neurodegenerative diseases

Environmental factors are responsible of cellular senescence and processes found in the development of cognitive disorders. The aim of this paper is to compare benefits of the Japanese, Mediterranean, and Argentinian Diet on the onset or prevention of senile dementia (SD) and Alzheimer's Disease (AD). Special focus was on the effects of specific compounds such as polyunsaturated fatty acids (PUFAs), antioxidants, and saturated and trans fatty acids. A high adherence to diets rich in PUFAs, monounsaturated fatty acids (MUFAs) and antioxidants may decrease the risk of developing neurodegenerative diseases; while the predominance of saturated and trans fatty acids possibly rises it.

Relative quantification of deuterated omega-3 and -6 fatty acids and their lipid turnover in PC12 cell membranes using TOF-SIMS

Understanding FA metabolism and lipid synthesis requires a lot of information about which FAs and lipids are formed within the cells. We focused on the use of deuterated substrates of 100 μM α-linolenic acid and linoleic acid to determine the relative amounts of their converted PUFAs and specific phospholipids that are incorporated into cell plasma membranes. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to image and analyze lipids in model cell membranes with and without FA treatment. Because of its high spatial resolution, TOF-SIMS can be used to simultaneously provide both chemical information and distribution of various molecules in the sample surface down to the subcellular scale. Data obtained from this analysis of isotopes in the cell samples were used to calculate the relative amounts of long-chain PUFAs and phospholipids from their precursors, α-linolenic acid and linoleic acid. Our results show that the FA treatments induced an increase in the amounts of α-linolenic acid and linoleic acid and their long-chain conversion products. Moreover, an enhanced level of phospholipid turnover of these FAs in lipids such as phosphatidylcholines, phosphatidylethanolamines, and phosphatidylinositols was also observed in the cell plasma membrane.

Current Perspectives and Mechanisms of Relationship between Intestinal Microbiota Dysfunction and Dementia: A Review

BACKGROUND

Accumulating data suggest a crucial role of the intestinal microbiota in the development and progression of neurodegenerative diseases. More recently, emerging reports have revealed an association between intestinal microbiota dysfunctions and dementia, a debilitating multifactorial disorder, characterized by progressive deterioration of cognition and behavior that interferes with the social and professional life of the sufferer. However, the mechanisms of this association are not fully understood.

SUMMARY

In this review, I discuss recent data that suggest mechanisms of cross-talk between intestinal microbiota dysfunction and the brain that underlie the development of dementia. Potential therapeutic options for dementia are also discussed. The pleiotropic signaling of the metabolic products of the intestinal microbiota together with their specific roles in the maintenance of both the intestinal and blood-brain barriers as well as regulation of local, distant, and circulating immunocytes, and enteric, visceral, and central neural functions are integral to a healthy gut and brain.

KEY MESSAGES

Research investigating the effect of intestinal microbiota dysfunctions on brain health should focus on multiple interrelated systems involving local and central neuroendocrine, immunocyte, and neural signaling of microbial products and transmitters and neurohumoral cells that not only maintain intestinal, but also blood brain-barrier integrity. The change in intestinal microbiome/dysbiome repertoire is crucial to the development of dementia.

Phenotypic heterogeneity of obesity-related brain vulnerability: one-size interventions will not fit all

Intact memory and problem solving are key to functional independence and quality of life in older age. Considering the unprecedented demographic shift toward a greater number of older adults than children in the United States in the next few decades, it is critically important for older adults to maintain work productivity and functional independence for as long as possible. Implementing early interventions focused on modifiable risk factors for cognitive decline at midlife is a strategy with the highest chance of success at present, bearing in mind the current lack of dementia cures. We present a selective, narrative review of evidence linking nutrition, body composition, vascular health, and brain function in midlife to highlight the phenotypic heterogeneity of obesity-related brain vulnerability and to endorse the development of individually tailored lifestyle modification plans for primary prevention of cognitive decline.

Emotion-Based Cognition in Mice Is Differentially Influenced by Dose and Chemical Form of Dietary Docosahexaenoic Acid

Docosahexaenoic acid (DHA) is a major constituent, and primary omega-3 fatty acid, in the brain. Evidence suggests that DHA consumption may promote cognitive functioning and prevent cognitive decline, and these effects may be particularly relevant in the context of fear or stress. However, the potency and efficacy of dietary DHA may depend on the form of DHA (e.g., phospholipid; PL vs. triglyceride; TG). In this study, we compared in mice the effects of consuming PL and TG forms of DHA on associative, avoidance (fear) based learning and memory. Diets consisted of either no DHA or 1%, 2%, and 4% PL- or TG-DHA. After 4 weeks on the test diets (n = 12/group), we used the 3-day passive avoidance (PA) and elevated plus maze (EPM) to examine fear and fear-associated learning and memory. We found a significant (p < 0.05) diet by time interaction in the PA and EPM. Compared to the control and the 1% TG-DHA group, mice consuming the diet supplemented with 1% PL-DHA displayed a significantly greater latency by test day 2 in the 3-day PA. No differences in latency between any of the groups were observed during trials 1 and 3. Mice consuming the 2% PL-DHA diet spent significantly more time frequenting the open arms during the first minute, but not the last 4 min, of the test. Compared to all other groups, mice fed the 4% TG-DHA diet had increased spleen, liver, and visceral fat weight. Consumption of the lower dose PL-DHA may confer enhanced efficacy, particularly on fear-based learning behavior.

Protective action of Omega-3 on paraquat intoxication in Drosophila melanogaster

Paraquat (PQ) (1,1'-dimethyl-4-4'-bipyridinium dichloride) is the second most widely used herbicide worldwide; however, in countries different sales and distribution remain restricted. Chronic exposure to PQ leads to several diseases related to oxidative stress and mitochondrial dysfunctions including myocardial failure, cancer, and neurodegeneration and subsequently death depending upon the dose level. The aim of this study was to examine if diet supplementation with eicosapentaenoic and docosahexaenoic acids (EPA and DHA, omega-3 long-chain fatty acids) serves a protective mechanism against neuromuscular dysfunctions mediated by PQ using Drosophila melanogaster as a model with focus on mitochondrial metabolism. PQ ingestion (170 mg/kg b.w. for 3 d) resulted in a decreased life span and climbing ability in D. melanogaster. In the brain, PQ increased thioflavin fluorescence and reduced either 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) nuclei staining and neuronal nuclei protein (NeuN) positive neurons, indicating amyloid formation and neurodegenetation, respectively. In the thorax, PQ ingestion lowered citrate synthase activity and respiratory functions indicating a reduction in mitochondrial content. PQ elevated Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) mRNA expression levels, indicative of high calcium influx from cytosol to mitochondrial matrix. In brain and thorax, PQ also increased hydrogen peroxide (H2O2) production and impaired acetylcholinesterase (AChE) activity. Concomitant EPA/DHA ingestion (0.31/0.19 mg/kg b.w.) protected D. melanogaster against PQ-induced toxicity preserving neuromuscular function and slowing down the rate of aging. In brain and thorax, these omega-3 fatty acids inhibited excess H2O2 production and restored AChE activity. EPA/DHA delayed amyloid deposition in the brain, and restored low citrate synthase activity and respiratory functions in the thorax. The effects in the thorax were attributed to stimulated mRNA expression level of genes involved either in mitochondrial dynamics or biogenesis promoted by EPA/DHA: dynamin-related protein (DRP1), mitochondrial assembly regulatory factor (MARF), mitochondrial dynamin like GTPase (OPA1), and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α). In conclusion, diet supplementation with EPA/DHA appears to protect D. melanogaster muscular and neuronal tissues against PQ intoxication.

Effect of docosahexaenoic acid on traumatic brain injury in rats

The present study aimed to investigate the protective effects of docosahexaenoic acid (DHA) on traumatic brain injury (TBI) in rats. A model of TBI was induced by lateral fluid percussion injury in adult rats and rats were randomly divided into the TBI-model group, TBI-low DHA group and TBI-high DHA group, while other healthy rats were assigned to the sham-operated group. Motor recovery was tested with beam-walking trials at 2, 7 and 15 days post-TBI. Cognitive recovery was tested with Morris water maze trials at 15 days post-TBI. The expression levels of caspase-3, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were measured by western blotting. DHA protected against motor deficits induced by TBI in beam walking tests. All TBI-model groups had longer escape latency and swimming distances than the sham groups. Compared with the TBI-low DHA group, the TBI-high DHA group demonstrated shorter escape latency and swimming distances. DHA inhibited the expression of caspase-3 and the inhibition effect was more obvious at a high dosage. Furthermore, DHA dose-dependently rescued neurons by upregulating the Bcl-2:Bax ratio. DHA supplementation was a viable strategy to mitigate injury from TBI.

Elucidating the link between the modifiable risk factors of Alzheimer's disease and neuroinflammation

Increased worldwide longevity through medical interventions, although beneficial, has allowed the age-related Alzheimer's disease (AD) to become an epidemic of the 21st century. AD pathology involves adverse activation of microglia, the immune cells of the brain and resulting chronic neuroinflammation. Certain diets, physical inactivity and Type 2 diabetes mellitus have been identified as the risk factors for developing AD, which may increase the risk of AD by neuroimmune mechanisms primarily through the overactivation of microglia. Thus, modifying these risk factors may represent an alternative therapeutic strategy for lowering the incidence of AD. We highlight the link between select modifiable risk factors and neuroimmune mechanisms, and demonstrate that by controlling microglial activation and neuroinflammation the prevalence of AD may be decreased.

Common neurodegenerative pathways in obesity, diabetes, and Alzheimer's disease

Cognitive decline in chronic diabetic patients is a less investigated topic. Diabetes and obesity are among the modifiable risk factors for Alzheimer's disease (AD), the most common form of dementia. Studies have identified several overlapping neurodegenerative mechanisms, including oxidative stress, mitochondrial dysfunction, and inflammation that are observed in these disorders. Advanced glycation end products generated by chronic hyperglycemia and their receptor RAGE provide critical links between diabetes and AD. Peripheral inflammation observed in obesity leads to insulin resistance and type 2 diabetes. Although the brain is an immune-privileged organ, cross-talks between peripheral and central inflammation have been reported. Damage to the blood brain barrier (BBB) as seen with aging can lead to infiltration of immune cells into the brain, leading to the exacerbation of central inflammation. Neuroinflammation, which has emerged as an important cause of cognitive dysfunction, could provide a central mechanism for aging-associated ailments. To further add to these injuries, adult neurogenesis that provides neuronal plasticity is also impaired in the diabetic brain. This review discusses these molecular mechanisms that link obesity, diabetes and AD. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

Nutrition and Inflammation in Older Individuals: Focus on Vitamin D, n-3 Polyunsaturated Fatty Acids and Whey Proteins

Chronic activation of the inflammatory response, defined as inflammaging, is the key physio-pathological substrate for anabolic resistance, sarcopenia and frailty in older individuals. Nutrients can theoretically modulate this phenomenon. The underlying molecular mechanisms reducing the synthesis of pro-inflammatory mediators have been elucidated, particularly for vitamin D, n-3 polyunsaturated fatty acids (PUFA) and whey proteins. In this paper, we review the current evidence emerging from observational and intervention studies, performed in older individuals, either community-dwelling or hospitalized with acute disease, and evaluating the effects of intake of vitamin D, n-3 PUFA and whey proteins on inflammatory markers, such as C-Reactive Protein (CRP), interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α). After the analysis, we conclude that there is sufficient evidence for an anti-inflammatory effect in aging only for n-3 PUFA intake, while the few existing intervention studies do not support a similar activity for vitamin D and whey supplements. There is need in the future of large, high-quality studies testing the effects of combined dietary interventions including the above mentioned nutrients on inflammation and health-related outcomes.

Serum metabolites from walnut-fed aged rats attenuate stress-induced neurotoxicity in BV-2 microglial cells

The shift in equilibrium towards excess reactive oxygen or nitrogen species production from innate antioxidant defenses in brain is a critical factor in the declining neural function and cognitive deficit accompanying age. Previous studies from our laboratory have reported that walnuts, rich in polyphenols, antioxidants, and omega fatty acids such as alpha-linolenic acid and linoleic acid, improve the age-associated declines in cognition and neural function in rats. Possible mechanisms of action of these effects include enhancing protective signaling, altering membrane microstructures, decreasing inflammation, and preventing accumulation of polyubiquitinated protein aggregates in critical regions of the brain. In the current study, we investigated whether the serum collected from aged animals fed with walnut diets (0, 6, and 9%, w/w) would enhance protection on stressed BV-2 microglia in vitro. In the growth medium, fetal bovine serum was substituted with the serum collected from 22-month-old rats fed per protocol for 12 weeks. Walnut diet serum (6 and 9%) significantly attenuated lipopolysaccharide-induced nitrite release compared to untreated control cells and those treated with serum from rats fed 0% walnut diets. The results also indicated a significant reduction in pro-inflammatory tumor necrosis factor-alpha, cyclooxygenase-2, and inducible nitric oxide synthase. These results suggest antioxidant and anti-inflammatory protection or enhancement of membrane-associated functions in brain cells by walnut serum metabolites.

Association of Seafood Consumption, Brain Mercury Level, and APOE ε4 Status With Brain Neuropathology in Older Adults

IMPORTANCE

Seafood consumption is promoted for its many health benefits even though its contamination by mercury, a known neurotoxin, is a growing concern.

OBJECTIVE

To determine whether seafood consumption is correlated with increased brain mercury levels and also whether seafood consumption or brain mercury levels are correlated with brain neuropathologies.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analyses of deceased participants in the Memory and Aging Project clinical neuropathological cohort study, 2004-2013. Participants resided in Chicago retirement communities and subsidized housing. The study included 286 autopsied brains of 554 deceased participants (51.6%). The mean (SD) age at death was 89.9 (6.1) years, 67% (193) were women, and the mean (SD) educational attainment was 14.6 (2.7) years.

EXPOSURES

Seafood intake was first measured by a food frequency questionnaire at a mean of 4.5 years before death.

MAIN OUTCOMES AND MEASURES

Dementia-related pathologies assessed were Alzheimer disease, Lewy bodies, and the number of macroinfarcts and microinfarcts. Dietary consumption of seafood and n-3 fatty acids was annually assessed by a food frequency questionnaire in the years before death. Tissue concentrations of mercury and selenium were measured using instrumental neutron activation analyses.

RESULTS

Among the 286 autopsied brains of 544 participants, brain mercury levels were positively correlated with the number of seafood meals consumed per week (ρ = 0.16; P = .02). In models adjusted for age, sex, education, and total energy intake, seafood consumption (≥ 1 meal[s]/week) was significantly correlated with less Alzheimer disease pathology including lower density of neuritic plaques (β = -0.69 score units [95% CI, -1.34 to -0.04]), less severe and widespread neurofibrillary tangles (β = -0.77 score units [95% CI, -1.52 to -0.02]), and lower neuropathologically defined Alzheimer disease (β = -0.53 score units [95% CI, -0.96 to -0.10]) but only among apolipoprotein E (APOE ε4) carriers. Higher intake levels of α-linolenic acid (18:3 n-3) were correlated with lower odds of cerebral macroinfarctions (odds ratio for tertiles 3 vs 1, 0.51 [95% CI, 0.27 to 0.94]). Fish oil supplementation had no statistically significant correlation with any neuropathologic marker. Higher brain concentrations of mercury were not significantly correlated with increased levels of brain neuropathology.

CONCLUSIONS AND RELEVANCE

In cross-sectional analyses, moderate seafood consumption was correlated with lesser Alzheimer disease neuropathology. Although seafood consumption was also correlated with higher brain levels of mercury, these levels were not correlated with brain neuropathology.

Molecular regulation of dendritic spine dynamics and their potential impact on synaptic plasticity and neurological diseases

The structure and dynamics of dendritic spines reflect the strength of synapses, which are severely affected in different brain diseases. Therefore, understanding the ultra-structure, molecular signaling mechanism(s) regulating dendritic spine dynamics is crucial. Although, since last century, dynamics of spine have been explored by several investigators in different neurological diseases, but despite countless efforts, a comprehensive understanding of the fundamental etiology and molecular signaling pathways involved in spine pathology is lacking. The purpose of this review is to provide a contextual framework of our current understanding of the molecular mechanisms of dendritic spine signaling, as well as their potential impact on different neurodegenerative and psychiatric diseases, as a format for highlighting some commonalities in function, as well as providing a format for new insights and perspectives into this critical area of research. Additionally, the potential strategies to restore spine structure-function in different diseases are also pointed out. Overall, these informations should help researchers to design new drugs to restore the structure-function of dendritic spine, a "hot site" of synaptic plasticity.

Components of a Mediterranean diet and their impact on cognitive functions in aging

BACKGROUND

Adhering to the Mediterranean diet (MeDi) is known to be beneficial with regard to many age-associated diseases including cardiovascular diseases and type 2 diabetes. Recent studies also suggest an impact on cognition and brain structure, and increasing effort is made to track effects down to single nutrients.

AIMS

We aimed to review whether two MeDi components, i.e., long-chain omega-3 fatty acids (LC-n3-FA) derived from sea-fish, and plant polyphenols including resveratrol (RSV), exert positive effects on brain health in aging.

CONTENT

We summarized health benefits associated with the MeDi and evaluated available studies on the effect of (1) fish-consumption and LC-n3-FA supplementation as well as (2) diet-derived or supplementary polyphenols such as RSV, on cognitive performance and brain structure in animal models and human studies. Also, we discussed possible underlying mechanisms.

CONCLUSION

A majority of available studies suggest that consumption of LC-n3-FA with fish or fishoil-supplements exerts positive effects on brain health and cognition in older humans. However, more large-scale randomized controlled trials are needed to draw definite recommendations. Considering polyphenols and RSV, only few controlled studies are available to date, yet the evidence based on animal research and first interventional human trials is promising and warrants further investigation. In addition, the concept of food synergy within the MeDi encourages future trials that evaluate the impact of comprehensive lifestyle patterns to help maintaining cognitive functions into old age.

Omega-3 polyunsaturated fatty acids ameliorate neuroinflammation and mitigate ischemic stroke damage through interactions with astrocytes and microglia

Omega-3 polyunsaturated fatty acids (PUFA n3) provide neuroprotection due to their anti-inflammatory and anti-apoptotic properties as well as their regulatory function on growth factors and neuronal plasticity. These qualities enable PUFA n3 to ameliorate stroke outcome and limit neuronal damage. Young adult male rats received transient middle cerebral artery occlusion (tMCAO). PUFA n3 were intravenously administered into the jugular vein immediately after stroke and 12h later. We analyzed stroke volume and behavioral performance as well as the regulation of functionally-relevant genes in the penumbra. The extent of ischemic damage was reduced and behavioral performance improved subject to applied PUFA n3. Expression of Tau and growth-associated protein-43 genes were likewise restored. Ischemia-induced increase of cytokine mRNA levels was abated by PUFA n3. Using an in vitro approach, we demonstrate that cultured astroglial and microglia directly respond to PUFA n3 administration by preventing ischemia-induced increase of cyclooxygenase 2, hypoxia-inducible factor 1alpha, inducible nitric oxide synthase, and interleukin 1beta. Cultured cortical neurons also appeared as direct targets, since PUFA n3 shifted the Bcl-2-like protein 4 (Bax)/B-cell lymphoma 2 (Bcl 2) ratio towards an anti-apoptotic constellation. Thus, PUFA n3 reveal a high neuroprotective and anti-inflammatory potential in an acute ischemic stroke model by targeting astroglial and microglial function as well as improving neuronal survival strategies. Our findings signify the potential clinical feasibility of PUFA n3 therapeutic treatment in stroke and other acute neurological diseases.

Fatty acid metabolism in carriers of apolipoprotein E epsilon 4 allele: is it contributing to higher risk of cognitive decline and coronary heart disease?

Apolipoprotein E (ApoE) is a protein playing a pivotal role in lipid homeostasis since it regulates cholesterol, triglyceride and phospholipid metabolism in the blood and the brain. APOE gene regulates the expression of this protein and has three different alleles: ε2, ε3 and ε4. Carrying an APOE4 allele is recognised as a genetic risk factor of late-onset Alzheimer’s disease (LOAD) and coronary heart disease (CHD). Consuming fatty fish, rich in long chain omega-3 fatty acids (LC omega-3), seems to be associated with risk reduction of developing LOAD and CHD but this link seems not to hold in APOE4 carriers, at least in LOAD. In CHD trials, APOE4 carriers supplemented with LC omega-3 were categorized as differential responders to the treatment with regards to CHD risk markers. This is potentially because fatty acid metabolism is disturbed in APOE4 carriers compared to the non-carriers. More specifically, homeostasis of LC omega-3 is disrupted in carriers of APOE4 allele and this is potentially because they β-oxidize more LC omega-3 than the non-carriers. Therefore, there is a potential shift in fatty acid selection for β-oxidation towards LC omega-3 which are usually highly preserved for incorporation into cell membranes.

Loss of MAP function leads to hippocampal synapse loss and deficits in the Morris Water Maze with aging

Hyperphosphorylation and accumulation of tau aggregates are prominent features in tauopathies, including Alzheimer's disease, but the impact of loss of tau function on synaptic and cognitive deficits remains poorly understood. We report that old (19-20 months; OKO) but not middle-aged (8-9 months; MKO) tau knock-out mice develop Morris Water Maze (MWM) deficits and loss of hippocampal acetylated α-tubulin and excitatory synaptic proteins. Mild motor deficits and reduction in tyrosine hydroxylase (TH) in the substantia nigra were present by middle age, but did not affect MWM performance, whereas OKO mice showed MWM deficits paralleling hippocampal deficits. Deletion of tau, a microtubule-associated protein (MAP), resulted in increased levels of MAP1A, MAP1B, and MAP2 in MKO, followed by loss of MAP2 and MAP1B in OKO. Hippocampal synaptic deficits in OKO mice were partially corrected with dietary supplementation with docosahexaenoic acid (DHA) and both MWM and synaptic deficits were fully corrected by combining DHA with α-lipoic acid (ALA), which also prevented TH loss. DHA or DHA/ALA restored phosphorylated and total GSK3β and attenuated hyperactivation of the tau C-Jun N-terminal kinases (JNKs) while increasing MAP1B, dephosphorylated (active) MAP2, and acetylated α-tubulin, suggesting improved microtubule stability and maintenance of active compensatory MAPs. Our results implicate the loss of MAP function in age-associated hippocampal deficits and identify a safe dietary intervention, rescuing both MAP function and TH in OKO mice. Therefore, in addition to microtubule-stabilizing therapeutic drugs, preserving or restoring compensatory MAP function may be a useful new prevention strategy.

n-3 LCPUFA improves cognition: the young, the old and the sick

Due to the implication of docosahexaenoic acid (DHA) in neurogenesis, synaptogenesis, neurite outgrowth and to its high incorporation into the brain, this n-3 long chain polyunsaturated fatty acid (LCPUFA) is considered as crucial in the development and maintenance of the learning memory performance throughout life. In the present chapter we aimed at reviewing data investigating the relation between DHA and cognition during the perinatal period, young adult- and adulthood and neurodegenerative diseases such as Alzheimer disease (AD). In Humans, dietary DHA supplementation from the perinatal period to adulthood does not reveal a clear and consistent memory improvement whereas it is the case in animal studies. The positive effects observed in animal models may have been enhanced by using n-3 PUFA deficient animal models as controls. In animal models of AD, a general consensus on the beneficial effects of n-3 LCPUFA in attenuating cognitive impairment was established. These studies make DHA a potential suitable micronutrient for the maintenance of cognitive performance at all periods of life.

Dietary fat composition and dementia risk

This is a qualitative review of the evidence linking dietary fat composition to the risk of developing dementia. The review considers laboratory and animal studies that identify underlying mechanisms as well as prospective epidemiologic studies linking biochemical or dietary fatty acids to cognitive decline or incident dementia. Several lines of evidence provide support for the hypothesis that high saturated or trans fatty acids increase the risk of dementia and high polyunsaturated or monounsaturated fatty acids decrease risk. Dietary fat composition is an important factor in blood-brain barrier function and the blood cholesterol profile. Cholesterol and blood-brain barrier function are involved in the neuropathology of Alzheimer's disease, and the primary genetic risk factor for Alzheimer's disease, apolipoprotein E-ε4, is involved in cholesterol transport. The epidemiologic literature is seemingly inconsistent on this topic, but many studies are difficult to interpret because of analytical techniques that ignored negative confounding by other fatty acids, which likely resulted in null findings. The studies that appropriately adjust for confounding by other fats support the dietary fat composition hypothesis.

Omega-3 polyunsaturated fatty acid supplementation improves neurologic recovery and attenuates white matter injury after experimental traumatic brain injury

Dietary supplementation with omega-3 (ω-3) fatty acids is a safe, economical mean of preventive medicine that has shown protection against several neurologic disorders. The present study tested the hypothesis that this method is protective against controlled cortical impact (CCI). Indeed, mice fed with ω-3 polyunsaturated fatty acid (PUFA)-enriched diet for 2 months exhibited attenuated short and long-term behavioral deficits due to CCI. Although ω-3 PUFAs did not decrease cortical lesion volume, these fatty acids did protect against hippocampal neuronal loss after CCI and reduced pro-inflammatory response. Interestingly, ω-3 PUFAs prevented the loss of myelin basic protein (MPB), preserved the integrity of the myelin sheath, and maintained the nerve fiber conductivity in the CCI model. ω-3 PUFAs also directly protected oligodendrocyte cultures from excitotoxicity and blunted the microglial activation-induced death of oligodendrocytes in microglia/oligodendrocyte cocultures. In sum, ω-3 PUFAs elicit multifaceted protection against behavioral dysfunction, hippocampal neuronal loss, inflammation, and loss of myelination and impulse conductivity. The present report is the first demonstration that ω-3 PUFAs protect against white matter injury in vivo and in vitro. The protective impact of ω-3 PUFAs supports the clinical use of this dietary supplement as a prophylaxis against traumatic brain injury and other nervous system disorders.

Unesterified docosahexaenoic acid is protective in neuroinflammation

Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possible that docosahexaenoic acid is anti-inflammatory in the brain as it is known to be in other tissues. Using a combination of models including the fat-1 transgenic mouse, chronic dietary n-3 polyunsaturated fatty acid modulation in transgenic and wild-type mice, and acute direct brain infusion, we demonstrated that unesterified docosahexaenoic acid attenuates neuroinflammation initiated by intracerebroventricular lipopolysaccharide. Hippocampal neuroinflammation was assessed by gene expression and immunohistochemistry. Furthermore, docosahexaenoic acid protected against lipopolysaccharide-induced neuronal loss. Acute intracerebroventricular infusion of unesterified docosahexaenoic acid or its 12/15-lipoxygenase product and precursor to protectins and resolvins, 17S-hydroperoxy-docosahexaenoic acid, mimics anti-neuroinflammatory aspects of chronically increased unesterified docosahexaenoic acid. LC-MS/MS revealed that neuroprotectin D1 and several other docosahexaenoic acid-derived specialized pro-resolving mediators are present in the hippocampus. Acute intracerebroventricular infusion of 17S-hydroperoxy-docosahexaenoic acid increases hippocampal neuroprotectin D1 levels concomitant to attenuating neuroinflammation. These results show that unesterified docosahexaenoic acid is protective in a lipopolysaccharide-initiated mouse model of acute neuroinflammation, at least in part, via its conversion to specialized pro-resolving mediators; these docosahexaenoic acid stores may provide novel targets for the prevention and treatment(s) of neurological disorders with a neuroinflammatory component. Our study shows that chronically increased brain unesterified DHA levels, but not solely phospholipid DHA levels, attenuate neuroinflammation. Similar attenuations occur with acute increases in brain unesterified DHA or 17S-HpDHA levels, highlighting the importance of an available pool of precursor unesterified DHA for the production of enzymatically derived specialized pro-resolving mediators that are critical in the regulation of neuroinflammation.

Current evidence for the clinical use of long-chain polyunsaturated n-3 fatty acids to prevent age-related cognitive decline and Alzheimer's disease

An NIH State of the Science Conference panel concluded in 2010 that insufficient evidence is available to recommend the use of any primary prevention therapy for Alzheimer's disease or cognitive decline with age. Despite the insufficient evidence, candidate therapies with varying levels of evidence for safety and efficacy are taken by the public and discussed in the media. One example is the long-chain n-3 (omega-3) polyunsaturated fatty acids (n-3 LC-PUFA), DHA and EPA, found in some fish and dietary supplements. With this report, we seek to provide a practical overview and rating of the level and type of available evidence that n-3 LC-PUFA supplements are safe and protective against cognitive aging and Alzheimer's disease, with additional discussion of the evidence for effects on quality of life, vascular aging, and the rate of aging. We discuss available sources, dose, bioavailability, and variables that may impact the response to n-3 LC-PUFA treatment such as baseline n-3 LC-PUFA status, APOE ε4 genotype, depression, and background diet. Lastly, we list ongoing clinical trials and propose next research steps to validate these fatty acids for primary prevention of cognitive aging and dementia. Of particular relevance, epidemiology indicates a higher risk of cognitive decline in people in the lower quartile of n-3 LC-PUFA intake or blood levels but these populations have not been specifically targeted by RCTs.

Omega-3 fatty acids in neurodegenerative diseases: focus on mitochondria

Mitochondrial dysfunction represents a common early pathological event in brain aging and in neurodegenerative diseases, e.g., in Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD), as well as in ischemic stroke. In vivo and ex vivo experiments using animal models of aging and AD, PD, and HD mainly showed improvement of mitochondrial function after treatment with polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA). Thereby, PUFA are particular beneficial in animals treated with mitochondria targeting toxins. However, DHA showed adverse effects in a transgenic PD mouse model and it is not clear if a diet high or low in PUFA might provide neuroprotective effects in PD. Post-treatment with PUFA revealed conflicting results in ischemic animal models, but intravenous administered DHA provided neuroprotective efficacy after acute occlusion of the middle cerebral artery. In summary, the majority of preclinical data indicate beneficial effects of n-3 PUFA in neurodegenerative diseases, whereas most controlled clinical trials did not meet the expectations. Because of the high half-life of DHA in the human brain clinical studies may have to be initiated much earlier and have to last much longer to be more efficacious.

The docosanoid neuroprotectin D1 induces homeostatic regulation of neuroinflammation and cell survival

The onset of neurodegenerations and nervous system injury both trigger cell signaling perturbations that lead to damage of neuronal circuits and synapic connections, as well as protective signaling that aims to halt disease onset. Here we review recent findings that support the role of the docosanoid mediator neuroprotectin D1 (NPD1) as an early response or sentinel during the initial phase of nervous system damage. NPD1 is derived from docosahexaenoic acid that is selectively concentrated and retained in the nervous system. The protein misfolding triggers the biosynthesis of NPD1 which in turn downregulates pathways that lead to cell death and changes the outcome to cell survival. Proteotoxic stress as a result of protein misfolding is a widespread event in many neurodegenerative diseases. Therefore, mechanisms and mediators such as NPD1 that curtail consequences of these events are of interest as leads in the search for novel preventive and or therapeutic approaches.

Marine omega-3 phospholipids: metabolism and biological activities

The biological activities of omega-3 fatty acids (n-3 FAs) have been under extensive study for several decades. However, not much attention has been paid to differences of dietary forms, such as triglycerides (TGs) versus ethyl esters or phospholipids (PLs). New innovative marine raw materials, like krill and fish by-products, present n-3 FAs mainly in the PL form. With their increasing availability, new evidence has emerged on n-3 PL biological activities and differences to n-3 TGs. In this review, we describe the recently discovered nutritional properties of n-3 PLs on different parameters of metabolic syndrome and highlight their different metabolic bioavailability in comparison to other dietary forms of n-3 FAs.

Primate aging in the mammalian scheme: the puzzle of extreme variation in brain aging

At later ages, humans have high risk of developing Alzheimer disease (AD) which may afflict up to 50% by 90 years. While prosimians and monkeys show more substantial changes, the great apes brains examined show mild neurodegenerative changes. Compared with rodents, primates develop and reproduce slowly and are long lived. The New World primates contain some of the shortest as well as some of the longest-lived monkey species, while the prosimians develop the most rapidly and are the shortest lived. Great apes have the largest brains, slowest development, and longest lives among the primates. All primates share some level of slowly progressive, age-related neurodegenerative changes. However, no species besides humans has yet shown regular drastic neuron loss or cognitive decline approaching clinical grade AD. Several primates accumulate extensive deposits of diffuse amyloid-beta protein (Aβ) but only a prosimian-the gray mouse lemur-regularly develops a tauopathy approaching the neurofibrillary tangles of AD. Compared with monkeys, nonhuman great apes display even milder brain-aging changes, a deeply puzzling observation. The genetic basis for these major species differences in brain aging remains obscure but does not involve the Aβ coding sequence which is identical in nonhuman primates and humans. While chimpanzees merit more study, we note the value of smaller, shorter-lived species such as marmosets and small lemurs for aging studies. A continuing concern for all aging studies employing primates is that relative to laboratory rodents, primate husbandry is in a relatively primitive state, and better husbandry to control infections and obesity is needed for brain aging research.

Neuroinflammation and proteostasis are modulated by endogenously biosynthesized neuroprotectin D1

Neurodegenerative diseases encompass complex cell signaling disturbances that initially damage neuronal circuits and synapses. Due to multiple protective mechanisms enacted to counteract the onset of neurodegenerative diseases, there is often a prolonged period without noticeable impairments during their initiation. Since severe cognitive deficit or vision loss takes place after that period there is an opportunity to harness endogenous protective mechanisms as potential therapeutic approaches. The activation of the biosynthesis of the docosanoid mediator neuroprotectin D1 (NPD1) is an early response to the upsurge of protein misfolding and other neuroinflammatory events. This overview discusses the potent neuroprotective and inflammation-modulating bioactivity of NPD1. This lipid mediator represents an early response to neurodegenerations, aiming to restore homeostasis.